InSb and HgCdTe are currently the most common materials for mid wavelength infrared detectors. They are both mature material technologies that allow imaging chips called Focal Plane Arrays (FPAs) with good quantum efficiencies, but they remain very expensive and require cooling. Over the past decade, the trend to dual color FPA to improve thermal imaging has increased complexity and cost. As an alternative to bulk materials, wavefunction engineering with epitaxial quantum wells and dots has also been explored with some success.
Colloidal quantum dots could present significant advantages over epitaxial dots. These quantum dots theoretically have a much higher packing density and an improved ease of processing, but the fundamental molecular vibrations of the organic surfactants inherent to the quantum dots are believed to block their applicability. These molecular vibrations, typically above 3 microns, introduce picosecond nonradiative recombination of the infrared electronic excitation. Still further, the large surface to volume ratio in colloidal quantum dot systems, which often induces quenching through unpassivated surfaces suggests their inoperability in mid wavelength detectors.